| Three experiments were conducted to determine the quality and safety characteristics of feed-grade calcium dihydrogen phosphate (MCP) and tricalcium phosphate (TCP) from different manufacturers and production processes, determine the quality and safety characteristics of feed-grade sodium dihydrogen phosphate (MSP). Thise study provided basis of experimental for the formulation of the national mandatory standard and rational use of MCP, TCP and MSP, and provided theoretical basis for rational use of three phosphats in feed production.Experiment1:Study on the quality and safety characteristics of feed-grade calcium dihydrogen phosphate from different manufacturers and production processes.This study surveyed MCP of10companies from representative areas of national. Researches were made on the quality characteristics of MCP by calcium precipitation method, calcium+sodium precipitation method and steam method, provided basis of experimental for the formulation of the national mandatory standard and rational use of MCP. Investigation indicators included quality characteristics:free water, crystal water, the number of crystal water, pH, undersize fraction (fineness), calcium, total phosphorus, water-soluble phosphorus, m(Ca)/m(P) and sulfate; safety characteristics: fluoride, arsenic, copper, iron, zinc, manganese, cadmium, chromium and lead.1) Quality characteristics:the contents of free water, crystal water, calcium, total phosphorus, water-soluble phosphorus and the number of crystal water, m(Ca)/m(P) and sulfate of the three processes are not significantly (P>0.05). The pH of steam method is significantly higher than calcium precipitation method and calcium+sodium precipitation method (P<0.05), the pH of calcium precipitation method is significantly higher than calcium+sodium precipitation method (P<0.05). The contents of0.5mm and0.4mm undersize fraction of steam method are significantly higher than calcium+sodium precipitation method (P<0.05).2) Safety characteristics:the contents of manganese, iron, zinc, chromium and lead of the three processes are not significantly (P>0.05). The content of fluoride of steam method is significantly lower than calcium precipitation method (P<0.05); the content of arsenic of steam method and calcium+sodium precipitation method is significantly lower than calcium precipitation method (P<0.05); The content of copper of steam method is significantly lower than calcium precipitation method (P<0.05); the content of cadmium of steam method and calcium+sodium precipitation method is significantly higher than calcium precipitation method (P<0.05).3) Comparison between manufacturers, there are significant differences among the part of security indicators of9samples (P<0.05).Experiments show that, in the three processes, to evaluate with quality characteristics:the content of water-soluble phosphorus, free water, crystal water, the number of crystal water and pH of steam method are highest, the contents of sulfate and all undersize fractions are lowest; the contents of free water and pH of calcium+sodium precipitation method are lowest, but total phosphorus and all undersize fractions are highest; the content of total phosphorus, water-soluble phosphorus and crystal water of calcium precipitation method are lowest, but the contents of calcium, m(Ca)/m(P) and sulfate are highest. To evaluate with safety characteristics:the removable efficiency of fluoride, arsenic and chromium of steam method are best, the contents of copper, iron and zinc are lowest, but the content of cadmium is highest; the contents of cadmium and lead of calcium+sodium precipitation method are lowest, the contents of manganese, iron and zinc are highest; the contents of fluoride, arsenic, copper, chromium and lead of calcium precipitation method are highest. In addition to the contents of0.5mm undersize fraction of steam method and calcium precipitation method are not according to GB/T22548-2008, the remaining indicators are qualified. There are some differences of the quality indicators of MCP, because of the different manufacturers and production processes. In addition to the national standards have been prescribed quality indicators, we should also be considered crystal water, the number of crystal water, m(Ca)/m(P), sulfate and also propose to reduce the requirements of fineness.Experiment2:Study on the quality and safety characteristics of feed-grade tricalcium phosphate from different production processes.This study surveys TCP of3companies from representative areas of national. Researches were made on the quality characteristics of TCP by high-temperature sintering method, chemical precipitation method and calcium phytate hydrolysis method, provided basis of experimental for the formulation of the national mandatory standard and rational use of TCP. Investigation indicators included quality characteristics:free water, calcium, total phosphorus, m(Ca)/m(P), citrate acid soluble phosphate, undersize fraction (fineness), pH, unsolvable in acid and sulfate; safety characteristics:fluoride, copper, iron, zinc, manganese, cadmium, chromium, lead and arsenic.1) Quality characteristics:the pH and content of0.009mm undersize fraction of the three processes are not significantly (P>0.05). the contents of free water, calcium and m(Ca)/m(P) of calcium phytate hydrolysis method are significantly higher than the others, the contents of total phosphorus and citrate acid soluble phosphate are significantly lower than the others (P<0.05); the contents of calcium and total phosphorus of high-temperature sintering method are significantly lower than chemical precipitation method, m(Ca)/m(P) is significantly higher than chemical precipitation method; the contents of free water and citrate acid soluble phosphate are not significantly between high-temperature sintering method and chemical precipitation method (P>0.05); the contents of0.180mm,0.154mm and0.125mm undersize fraction of calcium phytate hydrolysis method are significantly lower than the others (P<0.05); the contents of unsolvable in acid of calcium phytate hydrolysis method is lower than high-temperature sintering method (P>0.05), that of calcium phytate hydrolysis method and high-temperature sintering method are significantly higher chemical precipitation method (P<0.05); the content of sulfate of calcium phytate hydrolysis method is significantly lower than high-temperature sintering method, it is significantly higher than chemical precipitation method (P<0.05), that of high-temperature sintering method is significantly higher than the others (P<0.05).2) Safety characteristics:the content of copper of the three processes are not significantly (P>0.05). The content of fluoride of calcium phytate hydrolysis method is significantly higher than the others (P<0.05), that of high-temperature sintering method is significantly higher than chemical precipitation method (P<0.05); the contents of iron and manganese of calcium phytate hydrolysis method are significantly higher than the others (P<0.05); that of high-temperature sintering method are significantly higher than chemical precipitation method (P<0.05); the content of zinc of calcium phytate hydrolysis method and high-temperature sintering method are significantly higher than chemical precipitation method (P<0.05),but the content of zinc is not significantly between calcium phytate hydrolysis method and high-temperature sintering method (P>0.05); the contents of chromium, cadmium, lead and arsenic are significantly lower than the others (P<0.05), the content of chromium of high-temperature sintering method is significantly higher than chemical precipitation method and calcium phytate hydrolysis method (P<0.05), the contents of lead and arsenic of high-temperature sintering method are higher than chemical precipitation method (P>0.05), the content of cadmium of high-temperature sintering method is lower than chemical precipitation method (P>0.05).Experiments show that, in the three processes, to evaluate with quality characteristics:the contents of total phosphorus and citrate acid soluble phosphate of chemical precipitation method are highest, that of free water, m(Ca)/m(P), pH, unsolvable in acid and sulfate are lowest; the contents of calcium and m(Ca)/m(P) of calcium phytate hydrolysis method are highest, but the contents of total phosphate and citrate acid soluble phosphate are lowest; the contents of0.180mm undersize fraction, pH, unsolvable in acid and sulfate of high-temperature sintering method are highest. To evaluate with safety characteristics:the contents of fluoride, copper, iron, zinc, manganese and lead of chemical precipitation method are lowest; the content of fluoride, iron and manganese of calcium phytate hydrolysis method is highest, but the contents of cadmium, chromium, lead and arsenic are lowest; the contents of copper, zinc, chromium, lead and arsenic of high-temperature sintering method are highest. For the quality and safety of product, it is recommended that the indicators of national mandatory standard of feed-grade tricalcium phosphate:the content of calcium (Ca) is not less than30.0%, total phosphate (P) is not less than18.0%, m(Ca)/m(P) is1.50-2.10, free water is not less than1.0%, fluoride (F) is not more200mg/kg, arsenic (As) is not more than lOmg/kg, lead (Pb) is not more than30mg/kg, chromium is not more than30mg/kg, fineness (Over0.18mm test sieve) is not less than80%, unsolvable in acid is not less than10%, sulfate is not more than5.0%. In three processes, the contents of total phosphate, m(Ca)/m(P) and0.180mm undersize fraction of calcium phytate hydrolysis method does not comply with the parameters of the national mandatory standard of feed-grade tricalcium phosphate that we recommend.Experiment3:Study on the quality and safety characteristics of feed-grade sodium dihydrogen phosphateThis study surveyed MSP of9companies from representative areas of Sichuan Province that is the main producing areas, the production processes are phosphoric acid method, study on the quality and safety characteristics of feed-grade sodium dihydrogen phosphate, provided basis of experimental for the formulation of the national mandatory standard and rational use of MSP. Investigation indicators included quality characteristics:total phosphorus, pH, water insoluble matter, sulfate and loss on drying; safety characteristics:copper, iron, zinc, manganese, fluoride, arsenic, chromium, cadmium and lead.1) Among feed-grade phosphates, MSP is a high-quality feed grade phosphate, the content of phosphorus is higher, the content of fluorine, arsenic, lead, chromium, cadmium and other impurities are lower.2) For the quality and safety of product, it is recommended that the indicators of national mandatory standard of feed-grade sodium dihydrogen phosphate:the content of total phosphate (P) is25.3%-26.6%, water insoluble matter is not less than1.0%, pH (10g/L aqueous solution) is range from4.1to4.7, loss on drying (dihydrate, monohydrate and anhydrous) are20.0-25.0%、10.0-15.0%and≤2.0%respectively, fluoride (F) is not more500mg/kg, arsenic (As) is not more than10mg/kg, lead (Pb) is not more than30mg/kg, chromium is not more than30mg/kg, sulfate is not more than2.0%. |
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